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Warm-Cold Patterns Add to New Hampshire Weather Puzzle
DURHAM, N.H. -- Average monthly temperatures at Durham have been above normal 21 out of the past 22 months. Average monthly temperatures have been consistently above normal since June 1998 -- 15 straight months. Is global warming to blame?

No need to panic, says state climatologist Barry Keim, University of New Hampshire associate professor of geography. New Hampshire's up-and-down temperature patterns make for an interesting weather puzzle, and they're all part of the global system.

The city of Concord shows a similar pattern, with 20 straight months of above normal temperatures from December 1997 to July of this year, but the trend was snapped in August.

"These patterns are clearly related to global-scale circulation patterns," says Keim. "The atmosphere tends to favor certain patterns for some extended period, then it snaps into a new favored configuration. Each configuration can bring warmer or cooler than normal temperatures. Moreover, these favored patterns sometimes persist for weeks or months, and even years, as represented in the temperature records of Durham and Concord." vIs this a sign of global warming? Perhaps, says Keim, except Keene residents are left out in the cold. "No such warming pattern is evident at Keene," says Keim, who works at the UNH Climate Change Research Center, in the UNH Institute for the Study of Earth, Oceans, and Space. "In fact, over the past two years, Keene has been below normal more frequently than above normal. This shows how regional some of these patterns can be."

Although the results from Durham and Concord are impressive, are they record-setting? Close examination of the 104-year record of temperature at Durham shows that monthly mean temperatures were above normal from September 1930 to January 1932 -- 17 straight months. "This betters the current trend at Durham, but not Concord. However, the Durham string is still alive."

Keim also found:

14 straight warm months were recorded at Durham from July 1948 to August 1949, and again from November 1952 to December 1953.

More recently, Durham experienced 15 straight warm months from June 1990 to August 1991.

What about runs of cold months? "For some reason, runs of cold months don't seem to be as persistent," says Keim. However, Durham experienced 13 straight colder than normal months from June 1904 to June 1905, and had 14 out of 15 colder than normal months from June 1964 to August 1965.

"I'll take the warm temperatures over the cold anytime," concludes Keim, a New Orleans native.

By Carmelle Druchniak
UNH News Bureau